Expandable medical devices

ABSTRACT

A medical device with an expandable element and expandable tubular sleeve surrounding at least a portion of the expandable element which influences the rate, shape and/or force required to expand the expandable element and methods for use in a body lumen are provided.

BACKGROUND OF THE INVENTION

Vascular dilatation balloons on medical devices generally fall into twoclasses. The first class of vascular dilatation balloons comprises anoncompliant balloon formed from a relatively nondistensible materialsuch as polyethylene terephthalate (PET). Noncompliant balloons exhibita substantially uniform exterior inflated profile which remainssubstantially unchanged upon increasing inflation pressures.Noncompliant balloons have been suggested to be advantageous becausethey allow the introduction of increased inflation pressure to breakcalcified lesions while retaining a predictable inflation profile thusminimizing damage to the surrounding lumen. Non-limiting examples ofnoncompliant balloons are disclosed in U.S. Pat. No. 6,200,290 toBurgmeier and Published Application U.S. 2010/0022949 to Eidenschink.Additional examples are commonly known in the art.

The second class of vascular dilatation balloons comprises compliantballoons. Compliant balloons expand in diameter upon increased inflationpressure. A problem with compliant balloons has been that upon inflationwithin a lesion, the balloon inflates unevenly around the plaque to forman hour glass type shape. The uneven inflation of the compliant ballooncan result in damage to the lumen as well as failure to alleviate thestenosis. Non-limiting examples of compliant balloons are disclosed inU.S. Pat. No. 6,120,477 to Campbell et al. and U.S. Pat. No. 6,890,395to Simhambhatla, each of which is incorporated by reference herein inits entirety. Additional examples are commonly known in the art.

It is not uncommon with either types of balloons to have some difficultyin properly positioning the balloon, which are usually located on thedistal ends of catheters, within the region of the lesion of a patient'sartery or other body lumen or, if properly positioned within the lesion,to have difficulty in maintaining the position of the inflatable memberor balloon within the lesion during balloon inflation.

What is needed is a balloon which can be preferentially inflated indifferent sections to better control the position of the balloon and toprovide a more uniform pressure against the lesion during thedilatation. In addition, there is a need for a balloon that can bepreferentially inflated in different sections to more precisely expandan interventional device at the site of a lesion. Although U.S. Pat. No.5,470,313 and U.S. Pat. No. 5,843,116 disclose focalized intraluminalballoons with variable inflation zones or regions, the present inventionallows any type of balloon to be preferentially inflated at differentsections without modifying the balloon or delivery catheter.

SUMMARY OF THE INVENTION

An aspect of the present invention relates to a medical devicecomprising an elongated tubular body with a proximal and distal end, atleast one expandable element at the distal end of the elongated tubularbody, and an expandable tubular sleeve surrounding at least a portion ofthe expandable element. The expandable tubular sleeve comprises at leasttwo portions with differing radial strengths thereby influencing theshape of the expandable element and surrounding tubular sleeve and/orthe amount of force required to expand the expanding element and/orsurrounding tubular sleeve.

Another aspect of the present invention relates to a method of treatinga site in a body lumen. The method comprises providing a medical devicecomprising an elongated tubular body with a proximal and distal end, atleast one expandable element at the distal end of the elongated tubularbody, and an expandable tubular sleeve surrounding at least a portion ofthe expandable element. The expandable tubular sleeve comprises at leasttwo portions with differing radial strengths which influence the shapeand/or force required to inflate the expandable element and/orsurrounding expandable tubular sleeve. The medical device is positionedwithin a body lumen so that the expandable element in folded form isadjacent to a treatment site. The expandable element is then inflated ata pressure or force sufficient to inflate the expandable element at afirst portion of the expandable tubular sleeve. If needed, theexpandable element can be inflated at an increased pressure to inflatethe expandable element at a second portion of the expandable tubularsleeve with greater radial strength than the first portion.

The operation of the present invention should become apparent from thefollowing description when considered in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic illustration of an expandable element in expandedform of a medical device of the present invention.

FIG. 2 is a schematic illustration of an expanded element in folded formof a medical device of the present invention.

FIG. 3 is a schematic illustration of a medical device of the presentinvention with an expandable sleeve with regions of varying radialstrengths covering the folded expandable element.

FIG. 4 is schematic illustration of a medical device of the presentinvention expanded at a first portion.

FIG. 5 is a schematic illustration of medical device of the presentinvention expanded in full at first and second portions.

FIG. 6 is a side view of an expanded balloon showing typical dimensions.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to medical devices with an expandableportion for insertion into the body lumen. More particularly, thepresent invention relates to balloon dilatation catheters for insertionin the vascular system. In one embodiment, the balloon dilatationcatheter is a focal balloon dilatation catheter, meaning that expansiveenergy of the balloon is focused at one or more predetermined regionsalong the surface of the balloon.

Medical devices of the present invention comprise an elongated tubularbody with a proximal and distal end, at least one expandable element atthe distal end of the elongated tubular body, and an expandable tubularsleeve surrounding at least a portion of the expandable element.

One embodiment of the invention comprises a medical device comprising:an elongated tubular body with a proximal and distal end; (b) at leastone expandable element at the distal end of the elongated tubular body;and (c) an expandable tubular sleeve surrounding at least a portion ofthe expandable element, said expandable tubular sleeve comprising atleast two portions with differing compression ratios. In anotherembodiment, the expandable element is a balloon. In another embodiment,expandable element is self-expanding. In another embodiment, theexpandable element is mechanically expanded. In another embodiment, theexpandable element has a uniform thickness. In another embodiment, theexpandable tubular sleeve has a uniform wall thickness after expansion.In another embodiment, the expandable tubular sleeve has a uniform wallthickness prior to expansion.

Elements of the medical device of the present invention are depicted inFIGS. 1 through 5.

Specifically, FIGS. 1 and 2 are illustrative of a general ballooncatheter 100 having an elongated tubular body 102 with an expandableelement 104.

The elongated tubular body 102 has a proximal control end 106 and adistal functional end 108. The balloon catheter also has a proximalguidewire lumen 110 that extends through the length of the elongatedtubular body 102 and exits the distal end at a guide wire port 112. Theballoon catheter shown is an “Over The Wire” configuration, as commonlyknown in the art. As an alternate, the catheter could have amid-guidewire port and therefore have a “Rapid Exchange” configuration,as commonly known in the art. The balloon catheter 100 also incorporatesa proximal inflation port 114 that allows fluid communication betweenthe inflation port 114 and the inflatable element 104. The length andinner and outer diameter of the tubular body are selected based upon thedesired application of the medical device. For example, in onenonlimiting embodiment, wherein the medical device is used inpercutaneous transluminal coronary angioplasty, the length of thetubular body typically ranges from about 120 cm to about 140 cm. In thisembodiment, the outer diameter of the tubular body ranges from about0.026 inches to about 0.45 inches. As will be understood by the skilledartisan upon reading this disclosure, the length and/or diameter of thetubular body are in no way limiting and may be routinely modified forvarious applications of the medical devices of the present invention.The tubular body generally has a circular cross-sectional configuration.However, triangular and oval cross-sectional configurations can also beused.

The tubular body must have sufficient structural integrity to permit themedical device to be advanced to distal vascular locations withoutbending or buckling upon insertion. Various techniques are known formanufacturing the tubular bodies. In one embodiment, the tubular body ismanufactured by extrusion of a biocompatible polymer.

In another embodiment, the present invention comprises a catheter, anexpandable tubular sleeve, and an expandable member for expanding aninterventional device, said expandable member preferentially inflated atdifferent sections to better control the expansion of said implantablemedical device. Non-limiting examples of said interventional devices arestents (which include stent-grafts), and heart valves.

FIG. 1 shows the expandable element 104 in expanded form while FIG. 2shows the expandable element 104 in folded form.

As shown in FIGS. 3 through 5, the medical device of the presentinvention comprises an expandable tubular sleeve 300 surrounding atleast a portion of the expandable element 104. The expandable tubularsleeve comprises one or more materials having a porous microstructure.Examples of suitable materials include, but are not limited to expandedpolytetrafluoroethylene (ePTFE) and ultra high molecular weightpolyethylene (UHMW PE). Thus, in one embodiment, the expandable tubularsleeve comprises one or more materials having a porous microstructure.In another embodiment, the material is fibrillated. In anotherembodiment, the material comprises ePTFE. In another embodiment, thematerial is UHMW PE. In another embodiment, the expandable tubularsleeve is affixed to the expandable element.

The expandable tubular sleeve comprises at least two portions withdiffering radial strengths. In one embodiment, as depicted in FIGS. 3through 5, the expandable tubular sleeve 300 comprises a distal endportion 302 and a proximal end portion 304 with increased radialstrength as compared to a central or middle portion 306. In thisembodiment, as depicted in FIG. 4, the central portion 306 inflatesfirst under less expansion pressure while the distal end portion 302 andproximal end portion 304 expand second only under additional expansionpressure. In another embodiment, the differing radial strengths of theportions of the expandable sleeve influence the shape of the expandableelement and surrounding tubular sleeve. In another embodiment, thediffering radial strengths of the portions of the expandable sleeveinfluence the amount of force required to expand the sleeve.

The tubular expandable sleeve may comprise a single continuous material.In one embodiment, the single continuous material expandable sleeve iscomprised of a polymer having a node and fibril micro-structure. Referto U.S. Pat. No. 3,962,153, which is incorporated by reference herein inits entirety. A tube of such material can be placed onto a mandrel,longitudinally compressed and heat treated to preserve the compressedstate. Refer to U.S. Pat. No. 5,308,664, which is incorporated byreference herein in its entirety. The amount of longitudinal compressiondictates the amount of radial strength. More longitudinal compressionresults in a higher degree of radial strength (i.e. the highercompression ratio). A continuous tube can therefore have discrete zoneswith varying amounts of longitudinal compression (compression ratio)resulting in discrete zones of radial strength. The varied radialstrengths will then dictate the inflation profiles (or sequence) of anexpandable element.

A continuous tube having discrete zones of radial strength according tothe present invention can incorporate varying wall thicknesses andcross-sectional profiles. For example a continuous tube can have acircular, oval, triangular, square, rectangular or polygoncross-sectional shape. The tube can also incorporate wall sections ofvarying thickness. Various cross-sectional profiles and various wallthicknesses can be combined along a single tube.

Continuous tubes having discrete zones of radial strength according tothe present invention can also incorporate lubricious coatings, drugeluting coatings, anti-microbial coatings, visualization aids or otheradditions that enhance the device function.

Various “staged inflation” balloon profiles can be derived by the use ofan expandable sleeve that has discrete zones of varying radial strength.For example, a sleeve may be configured to have a weak (or easy toexpand) zone on one end of a balloon, combined with other zones ofstronger radial strength. Such a balloon would initially inflate on theone end (at a first pressure) and then progressively inflate along theballoon length at higher pressures. A balloon can have 2, 3, 4, 5, 6, 7,8, 9, 10 or more discrete zones of varying radial strength. The variousdiscrete zones of radial strength can be arranged along the balloon inany desired order. The radial strength of the discrete zones may also beindividually tailored to expand with any desired pressure. The discretezones of radial strength can be combined with non-expandable zones orwith zones of very low radial strength. Multiple sleeves having discretezones of radial strength can be combined in a longitudinal or co-axialconfiguration. An expandable sleeve having discrete zones of varyingradial strength can be positioned externally or internally to theexpandable element.

In one embodiment, the tubular expandable sleeve comprises ePTFE. It maybe desirable to modify the ePTFE used for the present invention byincorporating various additives with said ePTFE. Fillers can beincorporated in ePTFE by known methods, such as the methods taught byU.S. Pat. No. 5,879,794, to Korleski. Additives can also be imbibed intothe ePTFE by known methods. Additives can also be coated on the ePTFE byknown methods. Suitable additives include, for example, materials inparticulate and/or fiber form and can be polymers, adhesives,elastomers, ceramics, metals, metalloids, carbon, and combinationsthereof. Particularly useful additives include, for example, radiopaquematerials, such as certain metals (e.g. barium alloys) and carbon. Theadditives can be used in combination with desired adhesive materialswhen incorporated with the polymer. It may also be desirable to metalizethe ePTFE or at least a portion thereof. An additive may be included inthe matrix of the polymer itself, or contained within the voids definedby the polymeric structure, or both. Desirable fillers may also includecolorants, medicaments, anti-microbials, antivirals, antibiotics,antibacterial agents, anti-inflammatory agents, anti-proliferativeagents, anti-coagulating agents, hemostatic agents, analgesics,elastomers and mixtures thereof. Compounds which lubricate an ePTFEcover, thus allowing the material to slide smoothly across anothermaterial, can be used to coat, fill, or imbibe the tubular cover. Solidlubricants (i.e. graphite, waxes, silicone), fluid lubricants (i.e.hydrocarbon oils, silicone oils), gels (i.e. hydrogel) or any otherbiocompatible material known in the art may be used. In one embodiment,said expandable sleeve is coated, filled or imbibed on only one side. Inanother embodiment, said expandable sleeve is coated, filled or imbibedon both sides. In another embodiment, said expandable sleeve is coated,filled or imbibed on only one side and coated, filled or imbibed one theother side with a different material.

An expandable sleeve having discrete zones of radial strength, candictate the expansion profile or sequence of an underlying (oroverlying) expandable element. The controlled expansion profile orexpansion sequence can be used to enable or improve various medical andindustrial applications. For example, stents that are easilylongitudinally compressed during expansion can be expanded by theballoon and cover of the present invention. Said stent can be expandedfrom the center out, thus maintaining the stent longitudinally tensionedas it is expanded. An example of such a stent is described in U.S.Patent Application Publication U.S. 2009/0182413, incorporated byreference herein for all purposes. The longitudinal tension prevents thestent from being longitudinally compressed. In an opposite configurationthe balloon and cover can expand from the ends in towards the center andthereby compress the overlaying device. A heart valve stent may requirea stent that is expanded in a specific “hour-glass” shape, wherein thehour-glass shape is developed in a specific sequence. In otherapplications the expansion can begin at one end and progress to theopposing end of the expansible element, thereby creating a “pushing” orperistaltic motion. In one embodiment, said stents can comprise 316Lstainless steel, cobalt-chromium-nickel-molybdenum-iron alloy(“cobalt-chromium”), other cobalt alloys such as L605, tantalum,Nitinol, or other bio-compatible metals. In another embodiment, thestent can be a self expanding stent, a balloon expandable stent or acombination thereof.

In one embodiment, the thickness of the sleeve wall is selected to havea uniform wall thickness prior to expansion In another embodiment, thethickness of the sleeve wall is selected to have a uniform wallthickness after expansion In another embodiment, the thickness of thesleeve wall is selected to have a uniform wall thickness prior to andafter expansion.

The expandable tubular sleeve may be affixed to the expandable elementor may be slidably positioned around the expandable element without aseparate affixation means.

As shown in FIGS. 1 and 2, at least one expandable element 104 isprovided at the distal end of the tubular body. An example of anexpandable element useful in the present invention is an inflationballoon. Other forms of expandable elements include, but are not limitedto mechanical expanders such as “Chinese Lanterns”, expandable bow-arms,rotationally expandable/contractible coil springs, cam-type slidingmechanisms, expandable linkages, expandable collets, polymeric ornatural materials that expand when activated and other configurations ascommonly known in the art. The expandable element used in the medicaldevice of the present invention may also be self-expanding (eliminatedmechanically expand). In one embodiment, the expandable element has anouter wall of uniform thickness. The wall thickness can range from lessthan about 0.01 mm to about 5 mm. A typical 3 mm diameter thin wallednoncompliant balloon can have a wall thickness of about 0.02 mm.

The balloon members according to the present invention may be formedfrom using any materials known to those of skill in the art. Commonlyemployed materials include the thermoplastic elastomeric andnon-elastomeric polymers and the thermosets including the moisturecurable polymers.

Examples of suitable materials include but are not limited to,polyolefins, polyesters, polyurethanes, polyamides, polyimides,polycarbonates, polyphenylene sulfides, polyphenylene oxides,polyethers, silicones, polycarbonates, styrenic polymers, copolymersthereof, and mixtures thereof. Some of these classes are available bothas thermosets and as thermoplastic polymers. See U.S. Pat No. 5,500,181,for example. As used herein, the term copolymer shall be used to referto any polymeric material formed from more than one monomer.

As used herein, the term “copolymer” shall be used to refer to anypolymer formed from two or more monomers, e.g. 2, 3, 4, 5 and so on andso forth.

Useful polyamides include, but are not limited to, nylon 12, nylon 11,nylon 9, nylon 6/9 and nylon 6/6. The use of such materials is describedin U.S. Pat. No. 4,906,244, for example.

Examples of some copolymers of such materials include thepolyether-block-amides, available from Elf Atochem North America inPhiladelphia, Pa. under the tradename of PEBAX®. Another suitablecopolymer is a polyetheresteramide.

Suitable polyester copolymers, include, for example, polyethyeleneterephthalate and polybutylene terephthalate, polyester ethers andpolyester elastomer copolymers such as those available from DuPont inWilmington, Del. under the tradename of HYTREL®.

Block copolymer elastomers such as those copolymers having styrene endblocks, and midblocks formed from butadiene, isoprene,ethylene/butylene, ethylene/propene, and so forth may be employedherein. Other styrenic block copolymers include acrylonitrile-styreneand acrylonitrile-butadiene-styrene block copolymers. Also, blockcopolymers wherein the particular block copolymer thermoplasticelastomers in which the block copolymer is made up of hard segments of apolyester or polyamide and soft segments of polyether.

Specific examples of polyester/polyether block copolymers arepoly(butylene terephthalate)-block-poly(tetramethylene oxide) polymerssuch as ARNITEL® EM 740, available from DSM Engineering Plastics andHYTREL® polymers available from DuPont de Nemours & Co, alreadymentioned above.

Suitable materials which can be employed in balloon formation arefurther described in, for example, U.S. Pat. No. 6,406,457; U.S. Pat.No. 6,284,333; U.S. Pat. No. 6,171,278; U.S. Pat. No. 6,146,356; U.S.Pat. No. 5,951,941; U.S. Pat. No. 5,830,182; U.S. Pat. No. 5,556,383;U.S. Pat. No. 5,447,497; U.S. Pat. No. 5,403,340; U.S. Pat. No.5,348,538; and U.S. Pat. No. 5,330,428.

The above materials are intended for illustrative purposes only, and notas a limitation on the scope of the present invention. Suitablepolymeric materials available for use are vast and too numerous to belisted herein and are known to those of ordinary skill in the art.

Balloon formation may be carried out in any conventional manner usingknown extrusion, injection molding and other molding techniques.Typically, there are three major steps in the process which includeextruding a tubular preform, molding the balloon and annealing theballoon. Depending on the balloon material employed, the preform may beaxially stretched before it is blown. Techniques for balloon formationare described in U.S. Pat. No. 4,490,421, RE32,983, RE33,561 and U.S.Pat. No. 5,348,538.

The expandable element may be attached to the tubular body by variousbonding means known to the skilled artisan. Examples include, but arenot limited to, solvent bonding, thermal adhesive bonding and heatshrinking or sealing. The selection of the bonding technique isdependent upon the materials from which the expandable element andtubular body are prepared. Refer to U.S. Pat. No. 7,048,713 to Wang,which is incorporated by reference herein in its entirety, for generalteachings relating to the bonding of a balloon to a catheter.

Medical devices of the present invention are useful in treating sites ina body lumen or delivering interventional devices as described above. Inone embodiment, the medical device of the present invention is used inangioplasty procedure. In this method, the medical device of the presentinvention is percutaneously advanced so that the expandable element infolded form is adjacent to a vascular treatment site. Generally thetreatment site is a stenosis caused, for example, by plaque or athrombus. The expandable element of the medical device is then inflatedat a pressure or force sufficient to inflate the expandable element.After the stenosis is compressed to or beyond the native diameter of thelumen, the expandable element is evacuated and the medical device iswithdrawn from the body lumen. In another embodiment, said medicaldevices of the present invention are useful for delivering aninterventional device to a treatment site.

One embodiment of the invention comprises a method of treating a site ina body lumen, said method comprising the steps of positioning within abody lumen the medical device of the invention so that the expandableelement in folded form is adjacent to a treatment site; and inflatingthe expandable element at a pressure or force sufficient to inflate theexpandable element and to expand the expandable tubular sleeve accordingto its varying radial strength, as described above. In one embodiment,said expandable element expands an interventional device. In anotherembodiment, said interventional device is a stent. In anotherembodiment, said interventional device is a heart valve. In anotherembodiment, said treatment site is a coronary artery.

The following nonlimiting examples are provided to further illustratethe present invention.

EXAMPLE 1

A film tube was placed over a folded PET balloon. The film tube haddiscrete zones having different amounts of radial strength, imparted byvarying amounts of longitudinal compression. The middle zone of the filmtube was longitudinally compressed 35%. The ends of the film tube werelongitudinally compressed 60%. The resulting balloon inflated first inthe middle zone when a first pressure was applied to the balloon. Theends of the balloon inflated when a second, higher pressure was appliedto the balloon. The following example details a method of making aparticular “staged inflation” balloon.

An ePTFE film was helically wrapped around a mandrel having a diameterof about 28.5 mm and a length of about 37 cm. The film width was about2.54 cm. Two passes of film were wrapped in opposing directions, using a2.794 mm pitch (measured from adjacent film edges) with a film angle ofabout 78°. The wrapped length was about 30 cm.

The film wrapped mandrel was then placed into an air convection ovenheated to about 380° C. for about 28 minutes. This heat exposure bondedthe layers of ePTFE, forming a thin film tube.

The ePTFE film wrapped mandrel was removed from the oven, allowed tocool, and the thin film tube was removed from the mandrel. The thin filmtube had a diameter of about 28.5 mm and a wall thickness of about0.0254 mm.

The about 30 cm long thin film tube and was then tensioned by hand andstretched longitudinally to about 400% of the original length, or toabout 120 cm. After stretching, the tube was placed onto a mandrelhaving a diameter of about 4 mm and a length of about 130 cm. Thestretched tube was smoothed by hand onto the mandrel, forming a smalldiameter thin film tube having a diameter of about 4 mm.

A temporary ePTFE film was then helically wrapped onto the about 4 mmdiameter thin wall tube. The film thickness was about 0.00508 mm and thefilm width was about 1.905 cm. One pass of film was wrapped, using a2.6924 mm pitch (measured from adjacent film edges) with a film angle ofabout 78°.

The thin film tube and temporary ePTFE film wrap was then longitudinallycompressed. The middle portion of the thin film tube had an initiallength of 33.75 mm and was compressed to a length of 25 mm. The firstend of the thin film tube had an initial length of 44 mm and wascompressed to a length of 27.5 mm. The second end of the thin film tubewas longitudinally compressed in a similar manner to the first end ofthe thin film tube. The total length of the longitudinally compressedthin film tube was about 80 mm.

The longitudinally compressed thin film tube and mandrel was then placedinto an air convection oven heated to about 380° C. for about 1 minute.

The ePTFE film wrapped mandrel was then removed from the oven andallowed to cool.

The temporary ePTFE film wrap was then removed from the thin film tube.The resulting thin film tube had discrete zones of varying radialstrength.

The thin film tube was then placed over a catheter mounted, compactedPET balloon. The balloon is shown in an expanded state in FIG. 6. Thethin film tube having discrete zones of radial strength waslongitudinally centered onto the compacted balloon so that about 2 mm ofthe balloon legs protruded from the thin film tube. The ends of the thinfilm tube were secured to the balloon legs using 4981 LoctiteCyanoacrylate adhesive and 0.635 cm wide ePTFE film wrapped around boththe thin film tube and the balloon leg.

The balloon was then pressurized to about 3 atm, inflating the centersection of the balloon as depicted in FIG. 4. When further pressurizedto about 12 atm, the proximal and distal ends of the balloon inflated asshown in FIG. 5.

Numerous characteristics and advantages of the present invention havebeen set forth in the preceding description, including preferred andalternate embodiments together with details of the structure andfunction of the invention. The disclosure is intended as illustrativeonly and as such is not intended to be exhaustive. It will be evident tothose skilled in the art that various modifications may be made,especially in matters of structure, materials, elements, components,shape, size and arrangement of parts within the principals of theinvention, to the full extent indicated by the broad, general meaning ofthe terms in which the appended claims are expressed. To the extent thatthese various modifications do not depart from the spirit and scope ofthe appended claims, they are intended to be encompassed therein. Inaddition to being directed to the embodiments described above andclaimed below, the present invention is further directed to embodimentshaving different combinations of the features described above andclaimed below. As such, the invention is also directed to otherembodiments having any other possible combination of the dependentfeatures claimed below.

1. A medical device comprising: (a) an elongated tubular body with aproximal and distal end; (b) at least one expandable element at thedistal end of the elongated tubular body; and (c) an expandable tubularsleeve surrounding at least a portion of the expandable element, saidexpandable tubular sleeve comprising at least two portions withdiffering compression ratios.
 2. The medical device of claim 1, whereinthe expandable element is a balloon.
 3. The medical device of claim 1,wherein the expandable element is self-expanding.
 4. The medical deviceof claim 1, wherein the expandable element is mechanically expanded. 5.The medical device of claim 1, wherein the expandable element has auniform thickness.
 6. The medical device of claim 1, wherein theexpandable tubular sleeve has a uniform wall thickness after expansion.7. The medical device of claim 1, wherein the expandable tubular sleevehas a uniform wall thickness prior to expansion.
 8. The medical deviceof claim 1, wherein the expandable tubular sleeve is affixed to theexpandable element.
 9. The medical device of claim 1, wherein theexpandable tubular sleeve comprises one or more materials having aporous microstructure.
 10. The medical device of claim 9, wherein thematerial is expanded polytetrafluoroethylene.
 11. The medical device ofclaim 9, wherein the material is ultra high molecular weightpolyethylene.
 12. The medical device of claim 9, wherein the material isfibrillated.
 13. The medical device of claim 1, wherein differingcompression ratios of the at least two portions of the expandabletubular sleeve influence rate of expansion of the expandable element.14. The medical device of claim 1, wherein differing compression ratiosof the at least two portions of the expandable tubular sleeve influenceshape of the expandable element upon expansion.
 15. The medical deviceof claim 1, wherein differing compression ratios of the at least twoportions of the expandable tubular sleeve influence amount of forcerequired to expand the expandable element.
 16. The medical device ofclaim 1, wherein the expandable tubular sleeve is a single continuousmaterial.
 17. The medical device of claim 1, wherein the expandabletubular sleeve comprises a distal end portion, a proximal end portionand a central or middle portion.
 18. The medical device of claim 17,wherein the distal end portion and the proximal end portion exhibit withincreased compressive ratio as compared to the central or middleportion.
 19. A method of treating a site in a body lumen, said methodcomprising the steps of: positioning within a body lumen the medicaldevice of claim 1 so that the expandable element in folded form isadjacent to a treatment site; and expanding the expandable element at apressure or force sufficient to expand the expandable element at a firstportion of the expandable tubular sleeve.
 20. The method of claim 19,further comprising expanding the expandable element at an increased rateor pressure to expand the expandable element at a second portion of theexpandable tubular sleeve with greater compressive ratio than the firstportion.
 21. The method of claim 19, wherein said expandable elementexpands an interventional device.
 22. The method of claim 21, whereinsaid interventional device is a stent.
 23. The method of claim 21,wherein said interventional device is a heart valve.
 24. The method ofclaim 19, wherein said treatment site is a coronary artery.
 25. Themethod of claim 19, wherein the expandable element is a balloon.
 26. Themethod of claim 19, wherein said expandable tubular sleeves comprises atleast one polymer.
 27. The method of claim 26, wherein said polymer isexpanded polytetrafluoroethylene.